1. Field of the Invention
This invention relates to semiconductor memory devices and more particularly to vertical ROM devices.
2. Description of Related Art
U.S. Pat. No. 5,244,824 of Sivan for "Trench Capacitor and Transistor Structure and Method for Making the Same" shows a vertical channel memory cell for a DRAM.
Current flat type cells need to use a virtual ground technique to reduce effective cell size. Some problems with using such a virtual ground technique are as follows:
1) increase in chip size due to extra decoder circuits required for the virtual ground technique. PA1 2) slower speed results from the additional delays caused by extra decoder circuits.